1. Field of the Invention
This invention relates to methods and apparatuses for modifying intervertebral disc tissue and more particularly to the treatment of annular fissures using percutaneous techniques to avoid major surgical intervention.
2. Description of Related Art
Intervertebral disc abnormalities have a high incidence in the population and may result in pain and discomfort if they impinge on or irritate nerves. Disc abnormalities may be the result of trauma, repetitive use, metabolic disorders and the aging process and include such disorders but are not limited to degenerative discs (i) localized tears or fissures in the annulus fibrosus, (ii) localized disc herniations with contained or escaped extrusions, and (iii) chronic, circumferential bulging disc.
Disc fissures occur rather easily after structural degeneration (a part of the aging process that may be accelerated by trauma) of fibrous components of the annulus fibrosus. Sneezing, bending or just attrition can tear these degenerated annulus fibers, creating a fissure. The fissure may or may not be accompanied by extrusion of nucleus pulposus material into or beyond the annulus fibrosus. The fissure itself may be the sole morphological change, above and beyond generalized degenerative changes in the connective tissue of the disc. Even if there is no visible extrusion, biochemicals within the disc may still irritate surrounding structures. Disc fissures can be debilitatingly painful. Initial treatment is symptomatic, including bed rest, pain fillers and muscle relaxants. More recently spinal fusion with cages have been performed when conservative treatment did not relieve the pain. The fissure may also be associated with a herniation of that portion of the annulus.
With a contained disc herniation, there are no free nucleus fragments in the spinal canal. Nevertheless, even a contained disc herniation is problematic because the outward protrusion can press on the spinal nerves or irritate other structures. In addition to nerve root compression, escaped nucleus pulposus contents may chemically irritate neural structures. Current treatment methods include reduction of pressure on the annulus by removing some of the interior nucleus pulposus material by percutaneous nuclectomy. However, complications include disc space infection, nerve root injury, hematoma formation, instability of the adjacent vertebrae and collapse of the disc from decrease in height.
Another disc problem occurs when the disc bulges outward circumferentially in all directions and not just in one location. Over time, the disc weakens and takes on a xe2x80x9crollxe2x80x9d shape or circumferential bulge. Mechanical stiffness of the joint is reduced and the joint may become unstable. One vertebra may settle on top of another. This problem continues as the body ages and accounts for shortened stature in old age. With the increasing life expectancy of the population, such degenerative disc disease and impairment of nerve function are becoming major public health problems. As the disc xe2x80x9crollxe2x80x9d extends beyond the normal circumference, the disc height may be compromised, foramina with nerve roots are compressed. In addition, osteophytes may form on the outer surface of the disc roll and further encroach on the spinal canal and foramina through which nerves pass. This condition is called lumbar spondylosis.
It has been thought that such disc degeneration creates segmental instability which disturbs sensitive structures which in turn register pain. Traditional, conservative methods of treatment include bed rest, pain medication, physical therapy or steroid injection. Upon failure of conservative therapy, spinal pain (assumed to be due to instability) has been treated by spinal fusion, with or without instrumentation, which causes the vertebrae above and below the disc to grow solidly together and form a single, solid piece of bone. The procedure is carried out with or without discectomy. Other treatments include discectomy alone or disc decompression with or without fusion. Nuclectomy can be performed by removing some of the nucleus to reduce pressure on the annulus. However, complications include disc space infection, nerve root injury, hematoma formation, and instability of adjacent vertebrae.
These interventions have been problematic in that alleviation of back pain is unpredictable even if surgery appears successful. In attempts to overcome these difficulties, new fixation devices have been introduced to the market, including but not limited to pedicle screws and interbody fusion cages. Although pedicle screws provide a high fusion success rate, there is still no direct correlation between fusion success and patient improvement in function and pain. Studies on fusion have demonstrated success rates of between 50% and 67% for pain improvement, and a significant number of patients have more pain postoperatively. Therefore, different methods of helping patients with degenerative disc problems need to be explored.
FIGS. 1(a) and 1(b) illustrate a cross-sectional anatomical view of a vertebra and associated disc and a lateral view of a portion of a lumbar and thoracic spine, respectively. Structures of a typical cervical vertebra (superior aspect) are shown in FIG. 1(a): 104xe2x80x94lamina; 106xe2x80x94spinal cord; 108xe2x80x94dorsal root of spinal nerve; 114xe2x80x94ventral root of spinal nerve; 116xe2x80x94posterior longitudinal ligament; 118xe2x80x94intervertebral disc; 120xe2x80x94nucleus pulposus; 122xe2x80x94annulus fibrosus; 124xe2x80x94anterior longitudinal ligament; 126xe2x80x94vertebral body; 128xe2x80x94pedicle; 130xe2x80x94vertebral artery; 132xe2x80x94vertebral veins; 134xe2x80x94superior articular facet; 136xe2x80x94posterior lateral portion of the annulus; 138xe2x80x94posterior medial portion of the annulus; and 142xe2x80x94spinous process. In FIG. 1(a), one side of the intervertebral disc 118 is not shown so that the anterior vertebral body 126 can be seen. FIG. 1(b) is a lateral aspect of the lower portion of a typical spinal column showing the entire lumbar region and part of the thoracic region and displaying the following structures: 118xe2x80x94intervertebral disc; 126xe2x80x94vertebral body; 142xe2x80x94spinous process; 170xe2x80x94inferior vertebral notch; 110xe2x80x94spinal nerve; 174xe2x80x94superior articular process; 176xe2x80x94lumbar curvature; and 180xe2x80x94sacrum.
The presence of the spinal cord and the posterior portion of the vertebral body, including the spinous process, and superior and inferior articular processes, prohibit introduction of a needle or trocar from a directly posterior position. This is important because the posterior disc wall is the site of symptomatic annulus tears and disc protrusions/extrusions that compress or irritate spinal nerves for most degenerative disc syndromes. The inferior articular process, along with the pedicle and the lumbar spinal nerve, form a small xe2x80x9ctriangularxe2x80x9d window (shown in black in FIG. 1(c)) through which introduction can be achieved from the posterior lateral approach. FIG. 1(d) looks down on an instrument introduced by the posterior lateral approach. It is well known to those skilled in the art that percutaneous access to the disc is achieved by placing an introducer into the disc from this posterior lateral approach, but the triangular window does not allow much room to maneuver. Once the introducer pierces the tough annulus fibrosus, the introducer is fixed at two points along its length and has very little freedom of movement. Thus, this approach has allowed access only to small central and anterior portions of the nucleus pulposus. Current methods to not permit percutaneous access to the posterior half of the nucleus or to the posterior wall of the disc. Major and potentially dangerous surgery is required to access these areas.
U.S. Pat. No. 5,433,739 (the xe2x80x9c""739 patentxe2x80x9d) discloses placement of an RF electrode in an interior region of the disc approximately at the center of the disc. RF power is applied, and heat then putatively spreads out globally throughout the disc. The ""739 patent teaches the use of a rigid shaft which includes a sharpened distal end that penetrates through the annulus fibrosus and into the nucleus pulposus. In one embodiment the shaft has to be rigid enough to permit the distal end of the RF electrode to pierce the annulus fibrosus, and the ability to maneuver its distal end within the nucleus pulposus is limited. In another embodiment, a somewhat more flexible shaft is disclosed. However, neither embodiment of the devices of the ""739 patent permits access to the posterior, posterior lateral and posterior medial region of the disc, nor do they provide for focal delivery of therapy to a selected local region within the disc or precise temperature control at the annulus. The ""739 patent teaches the relief of pain by globally heating the disc. There is no disclosure of treating an annular tear or fissure.
U.S. Pat. No. 5,201,729 (the xe2x80x9c""729 patentxe2x80x9d) discloses the use of an optical fiber that is introduced into a nucleus pulposus. In the ""729 patent, the distal end of a stiff optical fiber shaft extends in a lateral direction relative to a longitudinal axis of an introducer. This prevents delivery of coherent energy into the nucleus pulposus in the direction of the longitudinal axis of the introducer. Due to the constrained access from the posterior lateral approach, stiff shaft and lateral energy delivery, the device of the ""729 patent is unable to gain close proximity to selected portion(s) of the annulus (i.e., posterior, posterior medial and central posterior) requiring treatment or to precisely control the temperature at the annulus. No use in treating an annular fissure is disclosed.
Accordingly, it is desirable to diagnose and treat disc abnormalities at locations previously not accessible via percutaneous approaches and without substantial destruction to the disc. It would further be desirable to be able to administer materials to a precise, selected location within the disc, particularly to the location of the annular fissure. It would be further desirable to provide thermal energy into collagen in the area of the fissure to strengthen the annulus and possibly fuse collagen to the sides of the fissure, particularly at the posterior, posterior lateral and the posterior medial regions of the inner wall of the annulus fibrosus.
Accordingly, an object of the invention is to provide a minimally invasive method and apparatus for diagnosing and treating fissures of discs at selected locations within the disc.
Another object of the invention is to provide an apparatus which is advanceable and navigable at the inner wall of the annulus fibrosus to provide localized heating at the site of the annular fissure.
Still a further object of the invention is to provide a device which has a distal end that is inserted into the disc and accesses the posterior, posterior lateral and the posterior medial regions of the inner wall of the annulus fibrosus in order to repair or shrink an annular fissure at such a location.
These and other objects of the invention have been accomplished by the present invention which provides methods for manipulating a disc tissue with a fissure or tear in an intervertebral disc, the disc having a nucleus pulposus and an annulus fibrosus, the annulus having an inner wall of the annular fibrosus. The method employs an externally guidable intervertebral disc apparatus, or catheter. The procedure is performed with a catheter having a distal end, a proximal end, a longitudinal axis, and an intradiscal section at the catheter""s distal end on which there is at least one functional element. The catheter is advanced through the nucleus pulposus and around an inner wall of an annulus fibrosus by applying a force to the proximal end, but the applied force is insufficient for the intradiscal section to puncture the annulus fibrosus. The next step is positioning the functional element at a selected location of the disc by advancing or retracting the catheter and optionally twisting the proximal end of the catheter. Then the functional unit treats the annular fissure.
A method of treating an intervertebral fissure comprises the steps of placing an energy source adjacent to the fissure and providing sufficient energy to the fissure to raise the temperature to at least about 45-70xc2x0 C. and for a sufficient time to cause the collagen to weld.
Yet another method of treating an intervertebral fissure comprises placing a catheter with a lumen adjacent to the fissure and injecting sealant into the fissure via the catheter lumen to seal the fissure.
In addition to the method, there is provided an externally guidable intervertebral disc apparatus for diagnosis or manipulation of disc tissue present at a selected location of an intervertebral disc, the disc having a nucleus pulposus, an annulus fibrosus, and an inner wall of the annulus fibrosus, the nucleus pulposus having a diameter in a disc plane between opposing sections of the inner wall. The apparatus comprises a catheter having a distal end, a proximal end, and a longitudinal axis, and an intradiscal section at the catheter""s distal end, which is extendible into the disc, has sufficient rigidity to be advanceable through the nucleus pulposus and around the inner wall of the annulus fibrosus under a force applied longitudinally to the proximal end, has sufficient flexibility in a direction of the disc plane to be compliant with the inner wall, and has insufficient penetration ability to be advanceable out through the annulus fibrosus under the force; and a functional element located at the intradiscal section for adding sufficient thermal energy at or near the fissure.